In the case of U.S. securities options, long contracts are automatically exercised by OCC at expiration if in-the-money by $0.01 or greater or if formally requested by the client prior to IBKR's 17:25 ET deadline.
OCC's rules require that all exercise and contrary exercise decisions be submitted by clearing members prior to the start of expiration processing, during which the clearing house randomly allocates long contract exercises to the holders of the short contracts. This processing cycle, therefore, does not afford the account holder the opportunity to first determine whether the short leg will be assigned prior to requesting exercise of the long leg in order to avoid delivery risk.
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